Water-based compositions, e.g., coating compositions such as paints, that include latex polymer particles or water-dispersible polymer particles typically also include a coalescent (i.e., coalescing agent or film-forming agent) in addition to pigments and fillers, for example. The coalescent functions as a solvent as well as a plasticizer for the polymer particles (to soften the polymer particles and assist in the formation of a continuous coating or film, for example, after applying it to a surface and allowing it to dry).
Useful coalescents are generally stable in the presence of water, compatible with other ingredients typically used in paint formulations, particularly the polymer particles, such that the stability of the water-based composition is not compromised. They are also typically sufficiently volatile to escape when the applied composition is allowed to dry, but sufficiently nonvolatile to evaporate more slowly than other ingredients that delay film formation (e.g., drying retarders, antifreezes). However, there is a general desire in the industry to reduce volatile organic emissions, thereby reducing the environmental and health concerns.
Although new and improved coalescents have been developed that provide low VOC compositions, such compositions can still be relatively soft and tacky. From the moment it is applied, a low VOC composition, such as a paint, seal coat, caulk, etc. is exposed to contamination from the atmosphere. This contamination includes dirt and dust that are carried to the surface by rain, airborne moisture droplets, wind currents or direct physical contact with people, animals or other objects. Dirt can be either organic or inorganic. Examples of dirt particles include sand, smoke particles, dust, metallic fibres, carbon black, rust, grease, pollen, human detritus, and fungal spores. Dirt particles attract moisture to the surface of the composition. This moisture provides a suitable environment in which microbial spores may survive and proliferate into colonies, thus further contributing to the unsightly appearance of the surface. Accordingly, water-based compositions can acquire a dirty and unsightly appearance because of the amount of air-borne dirt that clings to them. An effective dirt pick-up resistance technology which is suitable for low VOC compositions, and which does not compromise the required application and performance properties of surface finishes, is a common goal of the paint industry.